L11 revised Flashcards
what is the largest single tissue in the human body?
muscle
what are the 3 types of muscles present in the human body?
skeletal: striated , under voluntary nervous control
cardiac: striated , involuntary
and smooth : non striated, involuntary
describe the structure of striated muscles
a single muscle is composed of thousands of muscle fibers that extend for variable distance along its longitudinal axis
each muscle fiber is a large and complex multinucleated cell
what are muscle fibers surrounded by ?
an electrically excitable plasma membrane called the sarcolemma
what do individual muscle fibers contain ?
many myofibrils arranged in parallel embedded in intracellular fluid called sarcoplasm
what are the parallel structures inside individual muscle fibers called ?
myofibrils
what is the intracellular fluid inside individual muscle fibers called ?
sarcoplasm
what is the functional unit of muscle called?
sarcomere
where do T tubules invaginate from ?
sarcolemma
how does myofibril appear under the microscope ?
shows alternating dark(A bands ) and light(I bands ) bands
what region of the A band appears slightly lighter than the rest of the band ?
the central region of the A band , Which is also called the H band
what is the I band bisected by ?
very dense and narrow z line
where can thin filaments be found ?
in the I band . they also extend to the A band but not into the H zone
what proteins do thin filaments contain ?
actin , tropomyosin , and troponin
how are thin filaments arranged ?
they are arranged around the thick (myosin ) filaments as a hexagonal array
where can thick filaments be seen ?
confined to the A band
what protein do thick filaments contain ?
myosin
how are thick filaments arranged ?
cross section as a hexagonal array
what is monomeric actin called ?>
G actin \
it is globular
it makes up to 25% of muscle protein by weight
when does F actin form?
when G-actin polymerizes in the presence of Mg2+ to form the insoluble helicat filament called f actin
describe the structure of myosin
has a fibrous tail consisting of 2 intertwined helices
each helix has a globular head portion attached at one end
the hexamer consists of 2 heavy (H) chains and 4 light (L) chains
what is tropomyosin ?
fibrous molecule that consists of 2 chains , alpha , and beta , that attaches to F actin in the grooves between its filaments
it is present in all muscles and all muscles like structures
what is troponin ?
structure unique to skeletal muscles and consists of 3 poly peptides
what are the three polypeptides of troponin , briefly describe each ?
Troponin T : bind to tropomyosin as well as the 2 other troponin components
Troponin I:inhibits the F actin- myosin interaction , also binds to other components of troponin
troponin C : is a calcium binding polypeptide .
4 molecules of calcium ion are bound per molecule of troponin C
cardiac troponins help in diagnosing _____
myocardial infarction
MUSCLE CONTRACTION AND RELAXATION ARE IN THE OTHER DECK AND PPT
..
What is malignant hyperthermia ?
body temp rises on exposure to certain anesthetics and skeletal muscle relaxants
The reaction consists primarily of rigidity of skeletal muscles, hypermetabolism, and high fever.
what is the function of dystrophin ?
it is a cytoskeletal protein that connects F-actin to the DG complex(dystroglycan )
dystrophin complex acts as an anchor connecting each muscle cells cytoskeleton with the frame work of extracellular matrix proteins .Also play a role in cell signalling by interacting with chemical signals.
what happens if dystrophin is absent ?
In absence of dystrophin, plasma membrane of muscle cells gets damaged during contractile process leading to muscle cell death.
what term is applied to diseases that cause progressive weakness of skeletal muscles ?
muscular dystrophy
Mutations in the genes for the various components of the dystrophin–glycoprotein complex are a prominent cause.
Duchenne muscular dystrophy is ____?
is a serious form of dystrophy in which the dystrophin protein is absent from muscle
Becker muscular dystrophy is ___?
Dystrophin is present but altered or reduced in amount.
what is sarcopenia ?
Loss of skeletal muscle mass with age
